From 907985f48bc60818e291c631249f9bc84c83a06f Mon Sep 17 00:00:00 2001 From: Sasha Levin Date: Mon, 10 Jun 2013 15:18:00 -0400 Subject: slab: prevent warnings when allocating with __GFP_NOWARN Sasha Levin noticed that the warning introduced by commit 6286ae9 ("slab: Return NULL for oversized allocations) is being triggered: WARNING: CPU: 15 PID: 21519 at mm/slab_common.c:376 kmalloc_slab+0x2f/0xb0() can: request_module (can-proto-4) failed. mpoa: proc_mpc_write: could not parse '' Modules linked in: CPU: 15 PID: 21519 Comm: trinity-child15 Tainted: G W 3.10.0-rc4-next-20130607-sasha-00011-gcd78395-dirty #2 0000000000000009 ffff880020a95e30 ffffffff83ff4041 0000000000000000 ffff880020a95e68 ffffffff8111fe12 fffffffffffffff0 00000000000082d0 0000000000080000 0000000000080000 0000000001400000 ffff880020a95e78 Call Trace: [] dump_stack+0x4e/0x82 [] warn_slowpath_common+0x82/0xb0 [] warn_slowpath_null+0x15/0x20 [] kmalloc_slab+0x2f/0xb0 [] __kmalloc+0x24/0x4b0 [] ? security_capable+0x13/0x20 [] ? pipe_fcntl+0x107/0x210 [] pipe_fcntl+0x107/0x210 [] ? fget_raw_light+0x130/0x3f0 [] SyS_fcntl+0x60b/0x6a0 [] tracesys+0xe1/0xe6 Andrew Morton writes: __GFP_NOWARN is frequently used by kernel code to probe for "how big an allocation can I get". That's a bit lame, but it's used on slow paths and is pretty simple. However, SLAB would still spew a warning when a big allocation happens if the __GFP_NOWARN flag is _not_ set to expose kernel bugs. Signed-off-by: Sasha Levin [ penberg@kernel.org: improve changelog ] Signed-off-by: Pekka Enberg --- mm/slab_common.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'mm') diff --git a/mm/slab_common.c b/mm/slab_common.c index ff3218a0f5e1..2d414508e9ec 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -373,8 +373,10 @@ struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags) { int index; - if (WARN_ON_ONCE(size > KMALLOC_MAX_SIZE)) + if (size > KMALLOC_MAX_SIZE) { + WARN_ON_ONCE(!(flags & __GFP_NOWARN)); return NULL; + } if (size <= 192) { if (!size) -- cgit v1.2.3